The present invention relates to methods of stabilizing weakly consolidating subterranean formation intervals.
Hydrocarbon-bearing subterranean formations often contain one or more weakly consolidated intervals. As used herein, the term “weakly consolidated interval” (or “weakly consolidated target interval” or “weakly consolidated formation”) refers to one or more portions of a subterranean formation that contains loose particles and/or particles having insufficient bond strength to withstand the forces created by the production (or injection) of fluids through the formation during subterranean treatment operations. These particles may include, for example, sand, clay, or other fine particulate solids formed from the subterranean formation. A weakly consolidated interval may also be found in or near fractures in the subterranean formation. Some subterranean formations may initially be weakly consolidated or may become so due to pumping operations or production of fluids upward through the wellbore in the formation.
Weakly consolidated formations may contain substantial quantities of oil and gas, but recovery of the oil and gas is often difficult due to the movement of the loose particles. The movement of the loose particles imposes limitations on the drawdown pressure within the subterranean formation. As used herein, the term “drawdown pressure” refers to the differential pressure that drives fluids from within a wellbore to the surface. Therefore, loose particles limit the rate at which fluids can be produced from the subterranean formation.
One approach designed to prevent the movement of loose particles in a wellbore in a subterranean formation (or to “stabilize” or “consolidate”) is the use of gravel packing or frac-packing techniques. As used herein, the term “gravel packing” refers to a particulate control method in which a permeable screen is placed in a wellbore in a subterranean formation and the annulus between the screen and the formation surface is packed with gravel of a specific size designed to prevent the passage of loose particles from weakly consolidated intervals through the gravel packed screen, referred to as a “gravel pack.” As used herein, the term “frac-packing” refers to a combined hydraulic fracturing and gravel packing treatment. In such frac-packing operations, a substantially particulate-free fluid is generally pumped through the annulus between the permeable screen and the wellbore in the subterranean formation at a rate and pressure sufficient to create or enhance at least one fracture. Thereafter, a treatment fluid comprising particulates is pumped through the annulus between the permeable screen and the wellbore in the subterranean formation and the particulates are placed within the at least one fracture and in the annulus between the permeable screen and the wellbore in the subterranean formation, forming both a proppant pack and a gravel pack. In some embodiments, the treatment fluid comprising the particulates may be pumped at a rate and pressure sufficient to enhance the at least one fracture already formed.
In both gravel packing and frac-packing operations, loose particles may still escape the confines of the gravel pack and flow into the wellbore opening, limiting drawdown pressure. This may be particularly true if the loose particles have a particularly large size range, such that the gravel pack is not capable of preventing all loose particles from migrating through the pack.
Another technique for controlling the movement of loose particles in weakly consolidated formations involves treating the formation (or proppant particulates) with a consolidating agent to facilitate compaction of the loose particles within the formation and prevent them from migrating from the formation. However, consolidating agents are often difficult to handle, transport, and clean-up. For example, consolidating agents may cause damage to subterranean treatment equipment due to their inherent tendency to form a sticky or tacky surface.
Accordingly, an ongoing need exists for methods of stabilizing weakly consolidated subterranean formation intervals.